Blind, 24, was an integral part of Louis van Gaal's Netherlands side at the World Cup.

The versatile midfielder started all seven of his country's matches as they reached the semifinals in Brazil -- conceding just four goals -- and scored in the 3-0 win over Brazil in the third-place playoff in Brasilia.

Former Netherlands international Richard Witschge, part of manager Frank de Boer's coaching staff in Amsterdam, revealed that Blind had been training alone and said he felt that was in preparation for a move.

"I think Daley Blind will be leaving soon," Witschge told the website of Dutch sports magazine Helden. "I have a feeling. He has been training by himself. I think he has done that, because there's something going on."

Blind, who has also been linked with Barcelona, is the reigning Dutch Footballer of the Year after helping Ajax to win a fourth consecutive Eredivisie title last term.

He is usually deployed as a defensive midfielder by his club, but also played as a left wing-back and a left-sided centre-back for Van Gaal's Netherlands in Brazil.

United lack experienced cover for their three main centre-backs, Jonny Evans, Phil Jones and Chris Smalling, and although Ashley Young has impressed as a wing-back in preseason, there is no other proven alternative to new signing Luke Shaw.